Prevent submission of EditForm after disposal

Prevent submission of EditForm after disposal

Author: SteveSandersonMS

src/Components/Components/src/ComponentBase.cs

@@ -326,4 +326,7 @@ Task IHandleAfterRender.OnAfterRenderAsync()
         // have to use "async void" and do their own exception handling in
         // the case where they want to start an async task.
     }
+
+    // Exists for 6.0/7.0 patch only. A different solution is used from .NET 8 onwards.
+    internal bool IsComponentDisposed() => _renderHandle.IsComponentDisposed();
 }

src/Components/Components/src/RenderHandle.cs

@@ -70,4 +70,7 @@ private static void ThrowNotInitialized()
     {
         throw new InvalidOperationException("The render handle is not yet assigned.");
     }
+
+    // Exists for 6.0/7.0 patch only. A different solution is used from .NET 8 onwards.
+    internal bool IsComponentDisposed() => _renderer?.IsComponentDisposed(_componentId) ?? false;
 }

src/Components/Components/src/RenderTree/Renderer.cs

@@ -1119,4 +1119,8 @@ public async ValueTask DisposeAsync()
             }
         }
     }
+
+    // Exists for 6.0/7.0 patch only. A different solution is used from .NET 8 onwards.
+    internal bool IsComponentDisposed(int componentId)
+        => !_componentStateById.ContainsKey(componentId);
 }

src/Components/Web/src/Forms/EditForm.cs

@@ -136,6 +136,12 @@ private async Task HandleSubmitAsync()
     {
         Debug.Assert(_editContext != null);
 
+        // Exists for 6.0/7.0 patch only. A different solution is used from .NET 8 onwards.
+        if (IsComponentDisposed())
+        {
+            return;
+        }
+
         if (OnSubmit.HasDelegate)
         {
             // When using OnSubmit, the developer takes control of the validation lifecycle

src/Components/test/E2ETest/Tests/FormsTest.cs

@@ -809,6 +809,39 @@ public void CanHaveModelLevelValidationErrors()
         Browser.Collection(logEntries, x => Assert.Equal("OnValidSubmit", x));
     }
 
+    [Fact]
+    public async Task CannotSubmitEditFormSynchronouslyAfterItWasRemoved()
+    {
+        var appElement = MountSimpleValidationComponent();
+
+        var submitButtonFinder = By.CssSelector("button[type=submit]");
+        Browser.Exists(submitButtonFinder);
+
+        // Remove the form then immediately also submit it, so the server receives both
+        // the 'remove' and 'submit' commands (in that order) before it updates the UI
+        appElement.FindElement(By.Id("remove-form")).Click();
+
+        try
+        {
+            appElement.FindElement(submitButtonFinder).Click();
+        }
+        catch (NoSuchElementException)
+        {
+            // This should happen on WebAssembly because the form will be removed synchronously
+            // That means the test has passed
+            return;
+        }
+
+        // Wait for the removal to complete, which is intentionally delayed to ensure
+        // this test can submit a second instruction before the first is processed. Then
+        // wait a bit more to be really sure the second instruction was processed.
+        Browser.DoesNotExist(submitButtonFinder);
+        await Task.Delay(1000);
+
+        // Verify that the form submit event was not processed
+        Browser.DoesNotExist(By.Id("last-callback"));
+    }
+
     private Func<string[]> CreateValidationMessagesAccessor(IWebElement appElement, string messageSelector = ".validation-message")
     {
         return () => appElement.FindElements(By.CssSelector(messageSelector))

src/Components/test/testassets/BasicTestApp/FormsTest/SimpleValidationComponent.razor

@@ -1,6 +1,8 @@
 @using System.ComponentModel.DataAnnotations
 @using Microsoft.AspNetCore.Components.Forms
 
+@if (!removeForm)
+{
 <EditForm Model="@this" OnValidSubmit="@HandleValidSubmit" OnInvalidSubmit="@HandleInvalidSubmit" autocomplete="off">
     <DataAnnotationsValidator />
 
@@ -22,16 +24,20 @@
     </ul>
 
 </EditForm>
+}
 
 @if (lastCallback != null)
 {
     <span id="last-callback">@lastCallback</span>
 }
 
+<p><button id="remove-form" @onclick="RemoveForm">Remove form</button></p>
+
 @code {
     protected virtual bool UseExperimentalValidator => false;
 
     string lastCallback;
+    bool removeForm;
 
     [Required(ErrorMessage = "Please choose a username")]
     public string UserName { get; set; }
@@ -49,4 +55,10 @@
     {
         lastCallback = "OnInvalidSubmit";
     }
+
+    void RemoveForm()
+    {
+        removeForm = true;
+        Thread.Sleep(1000); // To ensure we can dispatch another event before this completes
+    }
 }